#!/usr/bin/env python
# encoding: utf-8

import sys

class Interaction():
    """Interaction class"""
    
    @classmethod
    def queryYesNo(self, question, default="yes"):
        """Ask a yes/no question via raw_input() and return their answer.
        
        "question" is a string that is presented to the user.
        "default" is the presumed answer if the user just hits <Enter>.
            It must be "yes" (the default), "no" or None (meaning
            an answer is required of the user).

        The "answer" return value is one of "yes" or "no".
        """
        valid = {"yes":"yes",   "y":"yes",  "ye":"yes",
                 "no":"no",     "n":"no"}
        if default == None:
            prompt = " [y/n] "
        elif default == "yes":
            prompt = " [Y/n] "
        elif default == "no":
            prompt = " [y/N] "
        else:
            raise ValueError("invalid default answer: '%s'" % default)

        while 1:
            sys.stdout.write(question + prompt)
            choice = raw_input().lower()
            if default is not None and choice == '':
                return default
            elif choice in valid.keys():
                return valid[choice]
            else:
                sys.stdout.write("Please respond with 'yes' or 'no' "\
                                 "(or 'y' or 'n').\n")
